The invention relates to a power supply unit or battery charging device. Power supply units convert currents or voltages from energy supply networks into currents or voltages suitable for the operation of electric units or devices. Battery charging devices are used for charging accumulators, for example, for mobile telephones, cordless telephones or portable computers.
The housing of a power supply unit or battery charging device is usually made of plastic, which is cost effective and guarantees an electrical insulation. A device cable that can be plugged into the power supply unit or battery charging device is used for setting up a connection to the device or accumulator respectively to be supplied with power.
U.S. Pat. No. 5,016,139 discloses a power supply unit in which the housing comprises two parts and is at least partly made of metal or plastic. The upper part of the housing has an area in the form of a grid of fins. The fins end in the plane of the upper part of the housing and have their base in a base area of substantially the same thickness, which is shaped so that it is complementary with the shape of two capacitors in the assembled power supply unit and holds them in a bracket device. The basic area has on the side facing the capacitors a coating that has a high coefficient of thermal conductivity, so that heat produced by the capacitors during the operation of the power supply unit is very well dissipated to the environment.
It is an object of the invention to provide a power supply unit which, having a compact structure, dissipates heat well to the environment during operation and, is also extremely handy.
The object is achieved in that the power supply unit or battery charging device has a housing with cooling fins, in which the cooling fins are arranged so that the interstices between the cooling fins are suitable for locking a cable of the device.
With such an embodiment of the unit, the cooling fins are used not only for cooling the device involved but, in addition, also for accommodating a cable which can be locked between the cooling fins (clamped), so that a compact handy unit is developed. Locking the cable of the device between the cooling fins is particularly advantageous for the transport of the device, because the cable is then not transported as a loose part and cannot be lost as a separate part during transport either. Only a respective distance between the cooling fins is to be guaranteed. Further additional material is not necessary.
More particularly, the housing is arranged as an injection molding plastic part and can be manufactured cost effectively, while the curving of the cooling fins is no problem.
To further improve the heat dissipation to the environment, there is proposed that on the inside of the housing a coating is deposited which has a high coefficient of thermal conductivity. A strong heating of the housing in small areas is avoided, so that also a guarantee may be given that a housing made of plastic exceeds the permissible maximum temperature of the plastic at no spot whatsoever. The coating having a high coefficient of thermal conductivity is, for example, a metallic coating which can be deposited on the inside of the housing of the device in an easy and cost effective manner. An additional effect is that the radiation of electromagnetic waves to the environment is reduced i.e. the EMV properties of the power supply unit or battery charging device are improved.
Alternatively, or in addition to an inside coating of the housing of the unit having a high coefficient of thermal conductivity, cooling fins may be arranged on the inside of the housing to promote the dissipation of heat from the inside of the housing to the environment.
In another embodiment is provided that the housing has recesses on the inside. They additionally increase the surface and also enhance the heat dissipation to the environment. They may be adapted to the device components to be installed on the inside of the housing i.e. they should be arranged closest possible to the inside of the housing.